A:   There are breed differences in age at which a bull could service a female. Brahman breeds tend to be later maturing than British and Continental breeds. Data out of MARC indicates that first sperm in beef males can be before they are a year of age (258 days of age) and age at which they produced 50 million sperm with at least 10% motility was about 300 days of age and their first completed mating was at slightly less than 365 days of age.